Tendon and ligament supports are well known in the field of equine medicine. They are used as a support system to prevent tendon and ligament injury and to facilitate the treatment of such tendon and ligament injury. One of the most delicate parts of a horse's anatomy is the area of the canon bone, fetlock joint and pastern regions of the lower leg beneath the knee and hock joints in particular the flexor tendons and suspensory ligaments are subject to strain injury. There are various causes of these injuries, all of which are well known to those engaged in the equine industry. The primary cause of such injury is generally over rotation of the fetlock joint for example, if a horse is excessively tired or unfit then the fetlock joint rotation can cause a dangerous level of tendon strain as it gallops at speed. It has been suggested that when tendon elongation is less than 8% of its relaxed length, there is no danger whatsoever to a horse and where the elongation exceeds 8% and progressively increases to 12% there is increasing stress until there is generally failure when the tendon elongation exceeds 12%. These figures must be taken as illustrative only because, obviously, the amount of tendon elongation will vary from horse to horse and the damage will also vary possibly depending on ambient conditions. However, these figures give some idea as to the approximate range of strain which needs to be considered.
The second major cause of equine tendon and ligament injury is over heating of the tendon material which in turn arises out of the dynamic loading experienced as a horse gallops. Recent research carried out by veterinary science institutions has concluded and published such conclusions which state that the heat generated within the superficial and deep digital flexor tendons and the suspensory and check ligaments of the horses lower leg during exercise is a significant factor in causing the onset of injury to this said anatomy. The studies show that the constant dynamic loading on these tendons and ligaments while the horse gallops causes an accumulation of heat that can reach 45° C. Collagen cells have viability only below a temperature of 42.5° C. Any temperature at or above 42.5° C. will result in irreparable necrotic damage to the collagen cells of which the tendon tissue is comprised. By reducing this build-up of temperature in the tendon and ligament group while exercising, cell necrosis is reduced and consequently the risk of injury to this anatomy can be significantly reduced.
Horse trainers frequently use existing boots and bandages for the purpose of protecting the horses legs against traumatic injuries caused by a strike impact from a hard object, most often a strike impact from another of the horse's legs. However these conventional boots or bandages, because they entirely cover the tendons while exercising, heat insulate the horses tendons and ligaments and prevent the aforementioned exercise induced heat from escaping to the outside air. FIG. 21 illustrates this problem where the heat transmits from the tendon core outward to the leg surface where it is blocked from further dissipation by the insulating effect of the conventional boot or bandage. Heat within the tendon core will then accumulate. Consequently the risk of heat injury to the tendons and ligaments is increased by the use of such heat insulating boots and bandages. The horse in nature is protected somewhat against such exercise induced heat build-up within the tendon and ligament cores, by the fact that as it gallops the cold air, passing unrestricted over the surfaces of the bare leg of the horse, takes with it a proportion of this said heat build up and thereby cools or reduces the core temperature of these tendons and ligaments. By using conventional boots and bandages this natural cooling method is lost.
A third major cause of tendon damage is when the tendons of the front leg are struck by the horse's hind leg. The horse's lower leg below the knee and hock joints, is also subject to a variety of traumatic injuries caused by a strike impact from a hard object, most often a strike impact from another of the horse's legs. These injuries include but are not limited to traumatic injury of the superficial digital flexor tendon, deep digital flexor tendon, the suspensory ligament, the check ligament, the extensor tendons, the skin, the synovial sheaths, the sesamoid bones, the coronet band and to the entire metacarpophalangeal joint area. There are in existence devices that are designed to protect the above-mentioned specific anatomy from a traumatic injury caused by a strike impact from another of the horse's legs. These conventional strike protection devices aim to shield the horse's legs from an impact and are at present constructed from one of the following materials: leather, plastics, rubber, woven fabric and non-rigid Kevlar. However it has been observed by veterinary surgeons that while these devices prevent penetration of the walls of the devices, they are not entirely effective at preventing injury. Indeed serious traumatic injuries to the aforementioned specific anatomy have continued to occur frequently despite the horses in question wearing these conventional devices at the time of injury. FIG. 28 illustrates this very problem which commonly occurs during an accidental over-reach while wearing one of the currently available devices. The hind leg can strike into the tendons of the front leg with an impact force in excess of 1000 Kg. It can be seen that the conventional strike prevention devices when struck by the hind leg at such forces, while they will prevent actual penetration of the impacting object through the wall of the device, they do not have sufficient stiffness and hardness to maintain their original shape. Consequently their shape deforms at the point of impact and the force is concentrated and effectively penetrates through to the fragile tendons and ligaments underneath. The result is inevitably a traumatic injury. The sources of impact include not only another of the horse's own legs but also can be from a fence which a horse is jumping, a polo mallet, a polo ball, the terrain or any other possible sources of external impact to which a horse could be exposed.
A further problem that occurs when a horse suffers a leg injury is that there is a high incidence of consequent tendon and ligament injury to the opposite leg as the animal takes the weight off the injured limb and places it all onto the opposite leg. Also, rotation of the fetlock joint can lead to a risk of carpal bone chip fracture.
In this specification the term “rotation” when used in relation to joints means pivoting or movement as would be the normal use of the joint and not as it is sometimes used to mean a twisting or other abnormal distortion of the joint. Thus, the terms “rotation” and “pivoting” are used interchangeably in this specification. Also the terms >“fetlock joint” and “metacarpophalangeal joint” refer to the same joint.
Many methods have been used to prevent or cure these problems and have heretofore been relatively inefficient and of limited or little use. For example, in GB-A-2,166,655 there is described and claimed a shock absorbing fetlock support of this general type, that can be best described as an auxiliary tendon support which is not in fact a full support system, even though it is described as such. It would undoubtedly absorb a certain amount of shock, but does not effectively limit rotation of the fetlock joint and hence tendon and ligament strain, which is an object of the present invention. The problem is that it does not take what is effectively the impact of the horse's hoof and the weight transmitted there through all of which is transmitted through the fetlock. This is because, in nature when the horse gallops, the hoof strikes the ground causing the fetlock joint travels downward towards the ground and while undoubtedly one of the problems is that this downward extension by the fetlock joint is transferred to the tendons and ligaments of the horse. The invention described in GB-A-2,166,655 would undoubtedly assist in protecting the fetlock joint but may not as suggested limit the strain on the tendons.
U.S. Pat. No. 5,579,627 describes a protection wrap for the horse's lower leg. In a laboratory experiment conducted by a major veterinary university in the UK to evaluate various non-rigid support systems for the equine metacarpophalangeal joint, this device was assessed as a means of supporting the metacarpophalangeal joint. It concluded that the device described by U.S. Pat. No. 5,579,627 had no significant effect in reducing tendon and ligament strain in horses. This is due to the fact that the soft materials from which it is constructed do not have sufficient strength and stiffness to cope with the immense forces of 2000-3000 Kg of tensile load on the flexor tendons as a horse exercises, whereas the invention described herein was proven to have a significant effect in reducing tendon and ligament strain in horses. U.S. Pat. Nos. 1,395,689; 3,209,517; 5,115,627; GB-A-1,153,613; GB-A-1,472,436 are representative of the prior art describing a similar form of boot used to protect a horse's foreleg from strikes by a hind leg, for example when galloping, but do not adequately prevent the fetlock and tendons being under constant stress.
GB-A-1,153,613 describes a support device with collars above and below the joint held together by an arrangement including an adjustable connecting strap at the back of the leg, but no hinge arrangement. While this provides a limited amount of support at a standstill, support during exercise is effectively not possible because the two collars will pull together under a tensile load.
U.S. Pat. No. 3,439,670 describes a brace for rigidly supporting knee and fetlock joints in animals. However, movement of a limited kind may be allowed by the provision of a spring-loaded hinge arrangement. The spring projects from brackets to the front of the horse's leg counteracting an articulated or hinted part of the brace to the sides of the horse's leg, to resist extension of the joint. However, this is an awkward arrangement because of the position of the spring to the front of the joint, which obstructs to the flexion of the joint, so that there is very little control of the degree of allowable movement, and no provision for any allowable sideways rotation at the fetlock joint. Also there may be a tendency for the upper part of the brace to slide upwards under load and lose its position, as there is nothing to hold the device in position along the back of the fetlock as the brace straightens out under load
Thus a need is identified for a tendon and ligament support that can effectively limit tendon and ligament strain as a horse exercises or rests by limiting the degree of rotation of the fetlock joint to a safe level and of which such support can be adjusted by the user.
Thus a need is identified for a tendon and ligament support applied to the horse's leg that will coot the said tendons and ligaments during exercise.
Thus a need is identified for a tendon and ligament support for the horse's leg that has the stiffness and strength to maintain its shape during the severest of strike impacts. It can therefore distribute the impact forces over a wider area and consequently significantly reduce the possibility of a strike injury. There is also identified a need for a strike impact protection device that can deflect the strike impact away from the horse's leg in the quickest possible time. This immediate deflection will further aid to protect the horse's leg.